A recent episode of the discovery channel show “How do they do it” discussed manufacture of spacesuits, and they discussed the use of chilled liquid for cooling. They said this use of chilled liquid was a relatively recent invention, and that the apollo astronauts said that wearing one of the apollo suits on the moon was about like being in a sauna.
When I first found out about the temperature on the moon I imagined me inside a space suit in a large tub of boiling water. I couldn’t imagine that thin suit keeping the heat out.
Now I get it!
Gotcha. As I said, was just curious.
-XT
Assuming a lake of what, methane?
Another way you can cool a spacesuit is by allowing a compressed gas to expand. Expanding gas has a cooling effect. People in spacesuits generally have another very good reason for wanting to crack open some gas cannisters, so it all works out pretty well.
Space suits currently deal with materials getting +250 deg F. This is for spacewalks, where the sun-side and shade-side changes every 45 minutes (90 min orbits).
constantine said:
That seems wrong. The LCGs were in use during Apollo.
http://lsda.jsc.nasa.gov/books/apollo/S6CH6.htm
Now maybe one didn’t have the system properly adjusted, or the sublimator wasn’t working right, or something.
What radiated heat?
Again… heat doesn’t radiate through a vacuum. The only way the heat of the surface gets to you is if you touch it, e.g. through your boots.
You do know that the ~ symbol means “approximately” not “negative,” right?
Nonsense. Every material above absolute zero radiates energy, vacuum or no.
<cleans spectacles>
Of course, it’s a tilde!
To the extent that heat’s a problem, body heat inside the suit is probably a bigger problem than anything external.
I once had a chat about this with some NASA guys. Of course the suits are refrigerated. The main problem is that there is always a face of the body which is exposed to the sun, and which gets quite warm, and one which is not, which tends to freeze. As a results, you end up sweating in one part of your body and being almost frozen on some other parts. Not fun.
Being around in space in a space suit is certainly a great experience in many respects, but it is a very exhausting one.
Incidentally, landing just after local morning also meant that the astronauts had strongly oblique lighting to highlight surface irregularities as the LEM was being maneuvered for landing.
Doesn’t radiative heat transfer require a medium to pass through? The way I understand it, radiation energy, like light from the sun is contained in the photons, but once it contacts and transfers energy to the molecules of the moon’s surface, that energy can only be transfered to something else (like an astronaut) by conduction, convection or radiation.
If the astronaut is standing still on the moon, then there is no atmosphere, and no wind, so convection is out.
The lack of atmosphere would mean, I think, that a hot moon rock 1 meter away from the astronaut would not be able to radiate heat to the astronaut since there is nothing between them to carry that energy from one body to the other (it is not the same as the heat from the sun, since the rock won’t radiate photons).
That only leaves conduction, and that requires direct contact to the moon, and is proportional to the surface area of the bottom of the spacesuit’s boots, and protecting against 100C via insulation seems pretty easy.
Am I on the right track here?
Although I’m thinking this simplifies things a little too much, since this only deals with the interaction of the astronaut and the moon, but the photons from the sun will also hit the astronauts directly. This can (and is) dealt with in the same way the spacesuit handles an EVA, though, and that’s clearly been managed.
ponders
The rock emits photons through exactly the same process that the Sun does. It’s just that, because the surface of the Moon is much cooler than the surface of the Sun, the photons emitted will be longer in wavelength, infrared rather than visible.
Hmmm, you’re right. I should have known that. Thanks for pointing it out to me!
Cold hands, in particular. In the 90’s NASA spent a decent chunk of change coming up with gloves with a battery-powered heating element in them, because astronauts on EVAs were having problems with their hands literally freezing.
The hands are a particularly challenging design item, because they have lower thermal mass so they retain heat less than, say the torso. Because they are required to have more articulation, so the number of layers is fewer and gloves thinner. And because they are extremeties, which means a proclivity for less blood flow and corresponding body heat.
Also, the gloves can be tiring to use because, even though they have constant volume joints (and thus are not as difficult to use as the Moon Landing Hoax proponents would have you believe), they still do require finger strength for prolonged activity.
Overall spacesuit thermal regulation is controlled by
- the suit being white, reflecting a lot of incoming radiation.
- the suit having a sublimator, which allows water to sublimate away, which cools water in the heat transfer system.
Balancing the interior temp to be comfortable is a challenge because exertion causes more body heat, different sunlight amounts means less radiation heating, and normal variations in body comfort levels. There are control knobs that each crew member sets individually and can adjust at will, but these only handle gross adjustments in cooling liquid flow rate, glove heating, air flow into helmet, etc.
Discovery Science has a series (that they repeat fairly often as it is more or less new) called Moon Machines. One of the episodes is about the space suits. It more or less says what has already been told here, but it doesn’t hurt to hear it with pictures and actual footage from those days when.
According to the 1958 documentary Missile to the Moon, stepping into direct sunlight could be extremely hazardous, as shown in official footage.